1. Field of the Invention
The present invention relates to positive displacement pumps, more particularly a positive displacement pump with displacement chambers, and displacement vanes, such that the displacement chambers and the displacement vanes establish a cyclical relative motion.
2. Related Art
Pumps of the general category of the present invention are known for example from German Pat. No. DT 22 30 773 to W. Gramm. However, it has been discovered that it is practically impossible to manufacture displacement chambers and displacement vanes with enough precision to ensure that, when driven with a rigid stroke, or a precise circular motion, the displacement vanes always follow closely to the walls of the displacement chambers thereby avoiding excessive strains or leaks. Further, with prior art pumps additional guide means are required to maintain the stability of the driven part in its desired position. Finally, the displacement chambers and displacement vanes of prior pumps are of such a shape that they interlock only over a section of about 270.degree. of the relative motion. It is therefore necessary to connect at least two of the displacement chambers in series with overlapping displacement regions in order to achieve a consistent displacement without leaks.